The syngeneic humoral immune responses of Lewis rats to intestinal mucins will be measured and their time-course traced. A new radioimmunoassay, based on the ethanol separation of antibody-bound (3H)-mucin from unbound labeled mucin, will be used to follow the responses. A new technique for isolating and purifying rat intestinal mucin will be used to prepare antigen for immunization and for labeling with tritium. Two methods will be used for tritiation -- one involving pre-oxidation followed by borohydride reduction by the van Lenten-Ashwell procedure, the other involving transfer of (3H)-sialyl-CMP by means of a specific glycosyl-transferase. (These procedures have already been used for the labeling of ovine, porcine, and bovine submaxillary mucins). The syngeneic responses of Lewis rats to their own gut mucins will be compared with responses to highly purified ovine, porcine, and bovine submaxillary and any cross-reactions noted. (It is anticipated that porcine mucine with its rich endowment of fucosyl groups will cross-react most heavily with rat intestinal mucins). The various end groups represented in the syngeneic rat antiserum reactions will be investigated by competitive inhibition studies involving the radioimmunoassay.